Conventionally, a substrate processing system for performing a film forming process, an etching process or the like on a semiconductor wafer (hereinafter, referred to as “wafer”) as a substrate includes a process module (hereinafter, referred to as “PM”) for receiving a wafer to perform a process thereon; an atmospheric transfer unit for taking out a wafer from a wafer cassette as a sealed chamber for storing a specified number of wafers; and a load-lock chamber located between the atmospheric transfer unit and the PM for transferring a wafer from the atmospheric transfer unit to the PM or vice versa.
In the conventional substrate processing system, process improvements of the individual devices included therein have been made in order to enhance the throughput that is calculated by wafer processing time. However, to meet the recent strong demands for a further throughput enhancement, in addition to the process improvements of the individual devices, active investigations are carried out to find methods of enhancing the efficiency by improving a coordination between the individual devices included in the substrate processing system in view of OEE (Overall Equipment Efficiency). In addition, to enhance the efficiency by improving the coordination between the individual devices, an external device for generally controlling the processes of the individual devices in the substrate processing system is also being developed.
As an apparatus for enhancing the efficiency by improving the coordination between the individual devices, there is known a throughput adjusting device used for a semiconductor manufacturing apparatus in which every process module has a gate valve that can be opened and closed by an operation of an air cylinder, wherein the semiconductor manufacturing apparatus is a single-wafer type apparatus including a plurality of process modules and a CCU (Central Control Unit) for controlling the operations of the process modules (for example, see Japanese Laid-Open Application No. H10-135093).
In this throughput adjusting device, a CPU in a CCU controls an electronic valve of an air cylinder to be closed and a timer counter T in a RAM in the CCU is operated to start to close a gate valve and at the same time to measure an actual operation time T1. Thereafter, when the gate valve is completely closed, the CPU substitutes the time measured by the timer counter T for an operation time T1, computes an idle time T2 by subtracting the operation time T1 from an operation monitoring time T0 read out from the RAM, and displays a current situation on a display in the throughput adjusting device. Thus, an operator can measure the operation time of devices easily and quickly, and the throughput of the semiconductor manufacturing apparatus can be enhanced by using the measured result and the like.
Furthermore, as a method of enhancing the efficiency by improving the coordination between the individual devices, there is known a method of determining manufacturing conditions by determining the number of surplus cassettes during the semiconductor manufacturing process, wherein a buffer size setting device computes S, i.e., the number of surplus wafers, from an OEE value calculated by using a specified formula based on the throughput of the manufacturing apparatus, the total number of the wafers, the time taken to mount and transfer the wafers, the number of the wafers kept in cassettes and the number of the cassettes, so that the number of the surplus cassettes are determined easily and precisely based on the computed S value (for example, see Japanese Laid-Open Application No. 2002-141255).
However, since the above-described device and method are to compute or predict an amount of the throughput that can be increased, they do not propose any substantial and specific techniques for enhancing the throughput. In other words, the above-described device and method propose little more than a conventional way of enhancing the throughput such as reducing idle times between individual steps during the manufacturing process based on the computed or predicted amount of the throughput that can be increased, and it is not possible to greatly enhance the throughput by using them because, while a specified device performs a specified operation, other devices not involved in the specified operation merely wait until moments for them to start their operations.